The measurement of different biological responses of the skin is of great importance in the activity and toxicity testing of molecules employed in skin product development. Various methods have been developed to assess the effects of compounds on the various skin features. These methods rely mainly on the measurement of changes in the expression of RNA or protein markers within treated skin cellular components (e.g. keratinocytes, dermal fibroblasts, melanocytes). Different markers are assessed as indicative endpoints of specific skin responses using mostly immunocytological and SkinAxis, LLC immunohistological approaches. These methodologies are offer often limited sensitivity, and are highly variable and difficult to objectively quantify. To circumvent these limitations, SkinAxis has developed the Quantitative Signaling (QuantiSig®) technology that allows the analysis of the activation of different pathways representative of specific biological responses of the skin in a reproducible, highly sensitive, and measurable fashion. QuantiSig® is a cell engineering technology that can be applied both in 2D cell cultures as well as in the reconstitution of 3-dimensional skin models without interfering with the normal physiological responses of the cells.
QuantiSig® allows the different cell types composing the skin tissue to stably carry a reporter gene whose expression is controlled by genetic elements activated during the stimulation of various pathways. The activation of the pathway following the application/exposure to chemical and biological compounds can then be monitored enzymatically in the engineered cells. Using different reporter genes, different cells and/or pathways can be evaluated at the same time. The QuantiSig® technology can be used to monitor the following cellular pathways in 2D cultures and reconstituted 3D tissues:
DNA Damage Response
QuantiSig-DDR® provides a very sensitive measurement of the DNA damage response pathway. The test can be applied to determine the effects of UV irradiation, sun protection applications on the DNA damage response pathway in skin as well as anti-cancer drug testing affecting the p53 pathway.
PPARs (PPARα, PPARβ/δ, and PPARγ) Pathway
QuantiSig-PPAR® identifies the activation of Peroxisome Proliferator-Activated Receptors (PPARs), members of the nuclear receptor family of ligand-activated transcription factors. The system detects all three-member subfamily PPARα, PPARβ/δ, and PPARγ, which control the expression of genes involved in lipid and carbohydrate metabolism, vascular biology, tissue repair, cell proliferation and differentiation. Testing of PPAR agonists is suitable for drug discovery applications for various conditions (e.g. diabetes, coronary artery disease, obesity, and cancer) and the identification of agents supporting cell regeneration.
Antioxidative Response
QuantiSig-AOR® allows to test the anti-oxidative response pathway involved in the modulation of the Nuclear factor erythroid-related factor 2 (Nrf2) and the expression of cytoprotective genes. Constitutive activation of Nrf2 has been found in many cancers, resulting in resistance against chemotherapy and radiotherapy in cancer cells. Thus, screening for Nrf2 inducers and inhibitors is important to develop therapies for stress-induced diseases including cancer, and for the identification of anti-oxidant components for skin care products.
XRE – Xenobiotic Responsive Element
QuantiSig-XRE® allows testing the activity of the aryl hydrocarbon receptor (AhR). AhR is a cytosolic ligand-activated transcription factor that directly interacts with drugs metabolites and environmental toxins collectively known as xenobiotics. This receptor is widely distributed in vertebrates and is expressed in skin cells, in which exogenous and endogenous ligands are abundant, where it is involved in the metabolism of xenobiotics as well as in the regulation of skin pigmentation and skin inflammation.